CONTROLS OF OROGENIC TECTONIC INHERITANCE ON THE INCEPTION AND PROPAGATION OF THE RED SEA RIFT

We applied integrated (structural analysis, remote sensing, bathymetry, aeromagnetic, and gravity) studies to examine the control of inherited structures on the Red Sea rift’s (RSR) geometry, segmentation, and kinematics and the temporal changes in rift segment obliquity relative to stress fields. The RSR separates the once contiguous Arabian and Nubian Shields (ANS); its coastlines align with significant crustal-scale shear zones and sutures within the ANS, suggesting structural control of the rift's geometry. The rift is divided into segments with orientations ranging from NW-SE to N-S, representing the basement fabrics in the ANS. We modeled the spatial and temporal variations in RSR obliquity using GPlates throughout two main rifting phases: (1) an early phase, starting at 24-22 Ma with near-perpendicular N45°W extension, and (2) a later phase, starting at 18-14 Ma, and continuing to the present. We used the continental oceanic boundary (COB) as a proxy for rift trend, the plate motion model in the Gplates for relative plate motion, and applied 1 Ma steps until the conjugate COBs no longer overlapped (end of rifting). Findings indicate: (1) during the early phase, NW-SE trending segments experienced low obliquity (0-20°) with extensional kinematics, while N-S trending segments showed moderate obliquity (40-50°) with transtensional conditions, (2) during the later phase, N-S trending segments experienced higher obliquity, resulting in significant strike-slip deformation. The inheritance effects are not restricted to the RSR segmentation and kinematic styles. The RSR Mid-Ocean Ridge (MOR) shows along-strike variations in geometry that correlate with segment obliquity relative to the stress field. In the Central segment of the rift, trending N-S, the MOR is lined with a series of en echelon closed deeps, interpreted as pull-apart basins, formed due to high obliquity in this segment. Inspection of N-S trending fault belts in NE Africa, formed by reactivation of basement fabric during the Red Sea rift opening, revealed partitioned transtensional deformation consistent with predicted kinematic styles during the early rifting phase. These findings demonstrate that the orientation of inherited structures relative to the stress field dictates kinematic styles along rift systems, resulting in a wide range of kinematic domains.